Crosslinked polymers containing urethane groups

ABSTRACT

A process for the production of mouldings, in particular contact lenses, in which a water-soluble, crosslinkable polymer is crosslinked in solution, and mouldings, in particular contact lenses, obtainable by this process; and novel water-soluble, crosslinkable polymers which can be employed in the crosslinking process, in particular those based on polyvinyl alcohol having a molecular weight of at least about 2000 which comprises units of the formulae: XI and XII, XI and XIII or XI, XII and XIII. In said Formulae, U is (a) or --Y--NH--CO--O--Z--O--CH═CH 2  group, and a unit of the formula XII and a unit of the formula XIII as defined in the description, and crosslinked polymers, either homopolymers or copolymers, made from these novel water-soluble, crosslinkable polymers, a process for the preparation of the novel water-soluble, crosslinkable polymers and the homopolymers and copolymers obtainable therefrom, mouldings made from said homopolymers or copolymers, in particular contact lenses made from these homopolymers or copolymers, and a process for the production of contact lenses using said homopolymers or copolymers.

The invention relates to a novel process for the production ofmouldings, in particular contact lenses, in which a novel crosslinkablepolymer comprising units containing a crosslinkable group and at leastone further modifier is crosslinked in solution, and to mouldings, inparticular contact lenses, which are obtainable by this process.

The present invention also relates to novel polymers based on polyvinylalcohol which contain cyclic acetal or ketal groups, and to novelcrosslinkable polymers which can be employed in the novel process, inparticular those based on starting polymers containing functionalgroups, for example hydroxyl groups, on the polymer chain or functionalgroups, for example imino groups, in the polymer chain or functionalgroups bonded to the polymer skeleton via a bridge, where thesefunctional groups allow covalent bonds to compounds containing acrosslinkable modifier group or another modifier group. These startingpolymers are, in particular, polyhydroxyl compounds having a 1,2- and/or1,3-diol structure, such as polyvinyl alcohol, or hydrolysed copolymersof vinyl acetate, for example copolymers with vinyl chloride,N-vinylpyrrolidone, etc.

The invention furthermore relates to crosslinked polymers, eitherhomopolymers or copolymers, made from these novel crosslinkable polymerswhich contain a crosslinkable group and at least one further modifier,to a process for the preparation of these novel crosslinkable polymersand the homopolymers and copolymers obtainable therefrom, to mouldingsmade from said homopolymers or copolymers, in particular contact lensesmade from these homopolymers or copolymers, and to a process for theproduction of contact lenses using the said homopolymers or copolymers.

Contact lenses based on polyvinyl alcohol have already been disclosed.For example, EP 216 074 discloses contact lenses comprising polyvinylalcohol containing (meth)acryloyl groups bonded via urethane groups. EP189 375 describes contact lenses comprising polyvinyl alcoholcrosslinked by means of polyepoxides.

Furthermore, some specific acetals containing crosslinkable groups havealso already been disclosed. In this connection, we refer, for example,to EP 201 693, EP 215 245 and EP 211 432. EP 201 693 describes, interalia, acetals of unbranched aldehydes having 2 to 11 carbon atomscarrying a terminal amino group which is substituted by a C₃ -C₂₄olefinically unsaturated organic radical. This organic radical containsa functionality which withdraws electrons from the nitrogen atom, andfurthermore the olefinically unsaturated functionality is polymerizable.EP 201 693 also claims products of the reaction of the acetalscharacterized above with a 1,2-diol, a 1,3-diol, a polyvinyl alcohol ora cellulose. However, such products are not described directly.

If one of the acetals of EP 201 693 is mentioned at all in connectionwith, for example, polyvinyl alcohol, as is the case, inter alia, inExample 17 of that patent application, the acetal which can bepolymerized via its olefinic group is first copolymerized with, forexample, vinyl acetate. The resultant copolymer is then reacted withpolyvinyl alcohol, and an emulsion having a solids content of 37%, a pHof 5.43 and a viscosity of 11,640 cps is obtained.

However, these references do not reveal the novel combination of acrosslinkable urethane structure with a second modifier having an acetalor urethane structure.

By contrast, the present invention relates, inter alia, in particular topolymers having, inter alia, a 1,2- and/or 1,3-diol skeleton, in which acertain percentage of the 1,3-diol units has been modified to give a1,3-dioxane and to give a urethane group, or in which a certainpercentage of the 1,3-diol units has been modified to give two differenturethane groups, where at least one group bonded via urethane contains acrosslinkable radical. The crosslinkable radical is, in particular, anacrylate or vinyl ether radical. The present invention likewise relatesto crosslinked homopolymers and copolymers of said crosslinkablepolymers, to a process for the preparation of novel crosslinkablepolymers and the homopolymers and copolymers obtainable therefrom, tomouldings made from said homopolymers or copolymers, in particularcontact lenses made from these homopolymers or copolymers, and to aprocess for the preparation of contact lenses using the saidhomopolymers or copolymers.

The novel crosslinkable polymer comprising a crosslinkable group and atleast one further modifier is preferably a derivative of a polyvinylalcohol having a mean molecular weight of at least about 2000 whichcomprises from about 0.5 to about 80%, based on the number of hydroxylgroups in the polyvinyl alcohol, of units of the formula XI ##STR1## andat least one further modifier comprising units of the formula formulaXII ##STR2## or units of the formula XIII ##STR3## in which U is an##STR4## or --Y--NH--CO--O--Z--O--CH═CH₂ group, X is a bridge having 2to 12 carbon atoms,

R₂ is hydrogen or a C₁ -C₄ alkyl group,

Y is a bridge having 7 to 12 carbon atoms,

Z is a C₂ -C₁₂ alkylene bridge, which may be interrupted once or morethan once by an oxygen atom,

R₃ is hydrogen, a C₁ -C₆ alkyl group or a cycloalkyl group,

R is a C₁ -C₁₂ alkylene bridge,

R₁ is an organic group having 1 to 18 carbon atoms,

A is an organic radical having 1 to 18 carbon atoms, and

m is 0 or 1.

The novel crosslinkable polymer comprising a crosslinkable group and atleast one further modifier is, in particular, a derivative of apolyvinyl alcohol having a molecular weight of at least about 2000 whichcomprises from about 0.5 to about 80%, based on the number of hydroxylgroups in the polyvinyl alcohol, of units, in particular, of the formulaV ##STR5## or of the formula VII ##STR6## or of the formula IX ##STR7##or of the formula X ##STR8## in which the symbols R₃, R, m, R₁, X, R₂,Y, Z and A are as defined above.

In the units of the formula V, VII, IX and X, the separation between twoOH groups which have been derivatized by means of a modifier group isnot crucial and is not defined by the separation given specifically inthe formulae. The essential feature of said formulae is that a polyvinylalcohol contains two different modifiers, as stated, without theirposition, number, sequence or separation being defined.

The polymer-bonded crosslinkable group and the further modifier arecovalently bonded to the polymeric support by an irreversible bond. Thefurther modifier serves, inter alia, for weighting, which, for example,improves the mechanical properties and increases the water content ofthe crosslinkable polymers.

If X is a bridge having 2 to 12 carbon atoms, it is, in particular, analiphatic, cycloaliphatic or aromatic bridge. Aliphatic bridges whichmay be mentioned in this connection are, in particular, alkylene, forexample ethylene, propylene, n-1-butylene, 2-butylene, n-amylene,1-hexylene, 1-heptylene, 1-octylene, 4-ethyl-2-hexylene, 1-nonylene,2-methylenepentane or 4-ethen-4-ylheptane. If X is a cycloaliphaticbridge, it is, in particular, cyclohexylene or cyclohexylene (loweralkylene), for example cyclohexylenemethylene, which is unsubstituted oris substituted by 1 to 4 methyl groups, for exampletrimethylcyclohexylenemethylene; if X is an aromatic bridge, it is, inparticular, phenylene, unsubstituted or substituted by lower alkylene orlower alkoxy, for example the phenylenemethylene or methylenephenylenegroup; further, it can also be a phenylenephenylene group.

X is preferably an aliphatic bridge, in particular C₁ -C₆ alkylene,especially --CH₂ --CH₂ --.

C₁ -C₄ Alkyl R₂ is a linear or branched alkyl group, such as the methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl group.

R₂ is preferably hydrogen or methyl.

If Y is a bridge having 7 to 12 carbon atoms, it is an aliphatic,cycloaliphatic or aromatic bridge. Aliphatic bridges Y are, for example,alkylene, for example 1-heptylene, 1-octylene or 1-nonylene. If Y is acycloaliphatic bridge, it is, in particular, cycloalkylene-C₁ -C₄alkylene, unsubstituted or substituted by C₁ -C₄ alkyl, in particularthe bridge of the formula ##STR9##

If Y is an aromatic bridge, it is, in particular, phenylene,unsubstituted or substituted by C₁ -C₄ alkyl, in particular the bridgeof the formula ##STR10##

Z as a C₂ -C₁₂ alkylene bridge which may also be interrupted by anoxygen atom is, in particular, an ethylene, propylene, n-1-butylene,n-2-butylene, n-amylene, 1-hexylene, 1-heptylene, 1-octylene or1-nonylene bridge. It is preferably a C₂ -C₄ alkylene bridge, inparticular an ethylene bridge.

R₃ as a C₁ -C₆ alkyl group is a linear or branched alkyl group which isunsubstituted or substituted, for example, by OH or halogen (Cl, Br, For I). It is, for example, a methyl, ethyl, n- or isopropyl group.

In the preferred units and crosslinkable polymers, R₃ is hydrogen, inwhich case the acetal group is involved, or R₃ is methyl or ethyl, inwhich case a ketal group is involved.

R as a C₁ -C₁₂ alkylene bridge is linear or branched, for examplemethylene, ethylene, propylene, n-1-butylene, 2-butylene, n-amylene,1-hexylene, 1-heptylene, 1-octylene, 4-ethyl-2-hexylene, 1-nonylene,2-methylenepentane or 4-ethen-4-ylheptane.

In the preferred polymers, R is, in particular, a linear C₁ -C₅ alkylenebridge, especially a C₁ -C₃ alkylene bridge, such as methylene, ethyleneor n-propylene.

R₁ as an organic group having 1 to 18 carbon atoms is a monovalentaliphatic, cycloaliphatic, aromatic or heterocyclic group.

R₁ as an aliphatic group having 1 to 18 carbon atoms is, for example, alinear or branched alkyl group, which is unsubstituted or substituted,for example by a heterocyclic group, by a carboxyl group or by an alkylcarboxylate group; however, this aliphatic group can also be an alkoxygroup, such as methoxy, or an alkoxyalkoxy group; however, the aliphaticgroup can also be an amino group of the formula ##STR11## in which R₆and R₇, independently of one another, are hydrogen or an unsubstitutedC₁ -C₆ alkyl group or a C₁ -C₆ alkyl group which is monosubstituted orpolysubstituted by, for example, COOH or COO(C₁ -C₄ alkyl).

R₆ and R₇ are preferably, independently of one another, hydrogen or amethyl group.

If R₁ is a cycloaliphatic group, it is, for example, cyclopentyl,cyclohexyl, methylcyclohexyl, 1,3-dimethylcyclohexyl,1-methyl-4-isopropylcyclohexyl, cycloheptyl or cyclooctyl.

If R₁ is an aromatic group, it is, in particular, a phenyl group, whichis unsubstituted or substituted (for example by halogen, C₁ -C₄ alkyl orC₁ -C₄ alkoxy).

If R₁ is a heterocyclic group, it is, in particular, a radical of afive-membered heterocyclic ring containing one ring member other thancarbon, such as --S--, --O-- or --NH--, for example furan, thiophene,pyrrole, pyrrolidone, pyroglutamic acid, maleimide of the formula##STR12## (in which R₉ and R₁₀, independently of one another, arehydrogen, C₁ -C₄ alkyl, in particular methyl, or aryl, such as phenyl,or halogen, such as F, Cl or Br; R₉ and R₁₀ are preferably hydrogen ormethyl), coumarone, thiocoumarone or indole; a five-memberedheterocyclic ring containing two ring members other than carbon, such as--O--, --S-- or --NH--, for example oxazole, isoxazole, thiazole,imidazole, hydantoin of the formula ##STR13## (in which R₆, R₇ and R₈,independently of one another, are hydrogen or a C₁ -C₆ alkyl group whichis unsubstituted or monosubstituted or polysubstituted by, for example,COOH or COO(C₁ -C₄ alkyl); a 5-membered heterocyclic ring containingthree or more ring members other than carbon, such as --O-- or --NH--for example furazan, 1,2,3-triazole, 1,2,4-triazole, 1,3,4-triazole ortetrazole; a 6-membered heterocyclic ring containing one ring memberother than carbon, for example --O--, --S-- or --NH--, for examplepyran, thiopyran, pyridine or quinoline; or a 6-membered heterocyclicring containing more than one ring member other than carbon, such as--N--, for example diazines, such as oiazine, miazine, dihydrouracil ofthe formula ##STR14## (in which R₈ is as defined above) or piazine,vicinal, asymmetrical or symmetrical triazine or 1,2,3,4-triazine,1,2,3,5-triazine or 1,2,4,5-triazine.

Preferred heterocyclic groups are radicals of five-membered heterocyclicrings containing one or two ring members other than carbon, inparticular --NH--, in particular those of imidazole, maleimide andpyrrolidone.

An organic radical A having 1 to 18 carbon atoms is an aliphatic,cycloaliphatic or aromatic radical. Particularly suitable aliphaticradicals are linear or branched alkyl groups, such as the methyl, ethyl,propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,heptadecyl and octadecyl groups; examples of suitable cycloaliphaticradicals are those listed under the symbol R₁ ; an aromatic group A is,for example, a phenyl group which is unsubstituted or substituted by,for example, C₁ -C₄ alkyl or C₁ -C₄ alkoxy.

If A is an aliphatic radical, this can be substituted by a heterocyclicgroup, suitable heterocyclic groups being, in principle, all thosedefined under R₁ which are bonded to the isocyanate radical --NCO, inparticular via a C₁ -C₆ alkyl group, especially via an ethyl group.

Preferred groups A are aliphatic C₁ -C₆ alkyl groups, in particularethyl and isopropyl, furthermore cyclohexyl and in particular C₁ -C₆alkyl which is substituted by a heterocyclic group, where theheterocyclic group is preferably a radical of a five-memberedheterocyclic ring containing one or two ring members other than carbon,in particular --NH--, in particular a radical of imidazole, maleimide orpyrrolidone. Particularly preferred groups A are, for example, those ofthe formulae ##STR15## in which R₄ is hydrogen or a C₁ -C₆ alkyl group,R₉ is as defined above, in particular hydrogen or methyl, R₁₀ and R₁₁,independently of one another, are hydrogen or a linear or branched C₁-C₁₂ alkyl radical, in particular a C₁ -C₅ alkyl radical, especially amethyl radical, and R₁₂ is a linear or branched C₁ -C₁₂ alkyl radical,which may be interrupted by an oxygen atom, in particular a methyl orethyl radical.

The preferred novel crosslinkable polymers comprising a crosslinkablegroup and at least one further modifier are, in particular, derivativesof a polyvinyl alcohol having a molecular weight of at least about 2000which comprises from about 0.5 to about 80%, based on the number ofhydroxyl groups in the polyvinyl alcohol, of, in particular, units ofthe formula V or IX.

The novel crosslinkable polymers comprising a crosslinkable group and atleast one further modifier are preferably derivatives of polyvinylalcohol having a mean molecular weight of at least about 2000 whichcomprises from about 0.5 to about 80%, in particular from about 1 to50%, further preferably from about 1 to 25%, preferably from about 2 to15%, particularly preferably from about 2 to 10%, based on the number ofhydroxyl groups of the polyvinyl alcohol, of units of the formula XI,XII and/or XIII. Novel crosslinkable polymers comprising a crosslinkablegroup and at least one further modifier which are intended for theproduction of contact lenses comprise, in particular, from about 0.5 toabout 25%, in particular from about 1 to 15%, particularly preferablyfrom about 2 to 12%, based on the number of hydroxyl groups of thepolyvinyl alcohol, of units of the formula XI, XII and/or XIII.

Polyvinyl alcohols which can be derivatized in accordance with theinvention preferably have a mean molecular weight of at least 10,000.The upper limit to their mean molecular weight is up to 1,000,000. Theypreferably have a mean molecular weight of up to 300,000, in particularof up to 100,000, very particularly preferably of up to about 70,000.

Polyvinyl alcohols which are suitable according to the invention usuallyprincipally have a poly(2-hydroxy)structure. However, polyvinyl alcoholsderivatized in accordance with the invention can also contain hydroxylgroups in the form of 1,2-glycols, such as copolymer units of1,2-dihydroxyethylene, as can be obtained, for example, by alkalinehydrolysis of vinyl acetate-vinylene carbonate copolymers.

In addition, the polyvinyl alcohols derivatized in accordance with theinvention can also contain small proportions, for example of up to 20%,preferably of up to 5%, of copolymer units of ethylene, propylene,acrylamide, methacrylamide, dimethacrylamide, hydroxyethyl methacrylate,methyl methacrylate, methyl acrylate, ethyl acrylate, vinylpyrrolidone,hydroxyethyl acrylate, allyl alcohol, styrene or similar comonomersusually used.

Polyvinyl alcohols (PVA) which can be used as starting polymers arecommercially available polyvinyl alcohols, for example Vinol® 107 fromAir Products (MW=22,000 to 31,000, 98-98.8% hydrolysed), Polysciences4397 (MW=25,000, 98.5% hydrolysed), BF 14 from Chan Chun, Elvanol® 90-50from DuPont and UF-120 from Unitika. Other producers are, for example,Nippon Gohsei (Gohsenol®), Monsanto (Gelvatol®), Wacker (Polyviol®) orthe Japanese producers Kuraray, Denki and Shin-Etsu. However, it isadvantageous to use Mowiol® products from Hoechst, in particular thoseof the 3-83, 4-88, 4-98, 6-88, 6-98, 8-88, 8-98, 10-98, 20-98, 26-88 and40-88 type.

The PVAs are prepared by basic or acidic, partial or virtually completehydrolysis of polyvinyl acetate.

As mentioned above, it is also possible to use copolymers of hydrolysedor partially hydrolysed vinyl acetate, which are obtainable, forexample, as hydrolysed ethylene-vinyl acetate (EVA), or vinylchloride-vinyl acetate, N-vinylpyrrolidone-vinyl acetate and maleicanhydride-vinyl acetate.

Polyvinyl alcohol is usually prepared by hydrolysis of the correspondinghomopolymeric polyvinyl acetate. In a preferred embodiment, thepolyvinyl alcohol derivatized in accordance with the invention comprisesless than 50% of polyvinyl acetate units, in particular less than 20% ofpolyvinyl acetate units. Preferred amounts of residual acetate units inthe polyvinyl alcohol derivatized in accordance with the invention are,based on the total amount of vinyl alcohol units and acetate units, fromabout 2 to 20%, preferably from about 2 to 16%, in particular from 2 to12%, especially from 0.5 to 3%.

The compounds comprising units of the formula V and also hydroxyl andacetate groups can be prepared in a manner known per se. For example, apolyvinyl alcohol having a mean molecular weight of at least about 2000which comprises units of the formula I

    --CH(OH)--CH.sub.2 --                                      (I)

can be reacted with from about 0.5 to 80%, based on the number ofhydroxyl groups in the polyvinyl alcohol, of a compound of the formulaII ##STR16## in which R₄ and R₅, independently of one another, arehydrogen or C₁ -C₆ alkyl, in particular methyl or ethyl and the othersymbols are as defined under the formula XII, in particular in an acidicmedium.

This gives a polyvinyl alcohol polymer containing acetal- orketal-bonded groups which conforms to the formula XII ##STR17## in whichthe symbols R₃, R, R₁ and m are as defined above.

The polymer of the formula XII is water-soluble and is isolated from thereaction solution, for example by precipitation in acetone.

In a second step, the polymer of the formula XII is reacted with anisocyanate compound of the formula IV ##STR18## which is known and inwhich the symbols X and R₂ are as defined above, for example2-isocyanatoethyl methacrylate, in an aprotic polar solvent at elevatedtemperature to give the crosslinkable polymer of the formula V.

Examples of suitable aprotic polar solvents are formamide,dimethylformamide (DMF), hexamethylphosphoric triamide (HMPT) and inparticular dimethyl sulfoxide (DMSO).

The term elevated temperature here is taken to mean a range of fromabout 20° to 100° C., in particular from 40° to 80° C., especially from75° to 80° C.

The acetals and ketals of the formula II and the polymer of the formulaXII are novel and represent a further subject-matter of the invention.

The acetals and ketals of the formula II in which m is 0 are obtained,for example, by reacting a bromoacetal/ketal of the formula ##STR19##for example 2-bromoacetaldehyde dimethyl acetal, with a compound R₁ --Hwhich introduces the group R₁, for example 5,5-dimethylhydantoin, at atemperature of from about 80° C. to 150° C. in an aprotic polar solvent,in particular DMF or DMSO, in the presence of anhydrous K₂ CO₃.

The acetals and ketals of the formula II in which m is 1 can be preparedby various methods, for example starting from a monocarboxylic acid R₁--COOH via 1,1'-carbonyldiimidazole and an aminoacetaldehyde alkylacetal by the following reaction scheme: ##STR20##

The reaction in the 1st step and also in the 2nd step is carried out inan organic solvent, for example tetrahydrofuran or dimethylformamide, ata temperature of from about 20° to 60° C.

Examples of suitable monocarboxylic acids R₁ --COOH are3-(2-oxopyrrolidin-1-yl)-propionic acid,3-(4,4-dimethyl-2,5-dioxoimidazolidin-1-yl)propionic acid and3-(3,5,5-trimethyl -2,4-dioxoimidazolidin-1-yl)propionic acid.

The acetal/ketal is in particular 2-aminoacetaldehyde dimethyl acetal.

Another method of preparing the acetals/ketals of the formula II inwhich m is 1 is a Michael addition of --NH--R₁ onto an α, β-unsaturatedcarbonyl compound, for example ##STR21## in the presence of a catalyst,for example a basic catalyst such as sodium ethoxide or pyridine, or aquaternary ammonium base, such as benzyltrimethylammonium hydroxide, oran alkali metal hydroxide (for example NaOH or KOH), or via an acidchloride, for example ##STR22## in an organic solvent, such astetrahydrofuran or dimethylformamide, at a temperature of from about 20°to 50° C.

The isolated polymer of the formula XII can be reacted analogously, in a2nd step, with a vinyl ether isocyanate of the formula VI

    CH.sub.2 ═CH--O--Z--O--CO--NH--Y--NCO                  (VI)

in which the symbols Z and Y are as defined above, in an aprotic polarsolvent at elevated temperature to give the crosslinkable polymer of theformula VII.

The isocyanates of the formula VI are novel and likewise represent afurther subject-matter of the invention.

These are obtained, for example, by reacting a hydroxyalkyl vinyl etherof the formula

    CH.sub.2 ═CH--O--Z--OH

with a diisocyanate of the formula

    OCN--Y--NCO

containing different reactive isocyanate groups (for example oneisocyanate group is sterically hindered and the other is not) in anaprotic polar solvent, such as DMSO, at a temperature of from about 20°C. to 80° C., if desired in the presence of a catalyst, such asdibutyltin dilaurate, a tertiary amine, such asN,N-dimethylcyclohexylamine or N,N-dimethylbenzylamine.

The polymers comprising crosslinkable units of the formulae V and VIIare thus crosslinkable polymers containing a crosslinkable group(meth)acrylate or vinyl ether group! bonded via urethane and anacetal/ketal group as further modifier.

The urethane-urethane-modified crosslinkable polymers comprising unitsof the formula IX are obtained by reacting a polyvinyl alcohol having amolecular weight of at least about 2000 which comprises units of theformula I

    --CH(OH)--CH.sub.2 --                                      (I)

and also acetate groups with from about 0.5 to 80%, based on the numberof hydroxyl groups in the polyvinyl alcohol, of an isocyanate of theformula IV ##STR23## and an isocyanate of the formula VIII

    A--NCO                                                     (VIII)

in which the symbols R₂, X and A are as defined above, in a one-potprocess in an aprotic polar solvent at elevated temperature.

Suitable aprotic polar solvents are those already mentioned inconnection with the preparation of the polymers of the formula V; thesame applies to the elevated temperature.

Whereas the isocyanates of the formula IV are known, for example2-isocyanatoethyl methacrylate, and can be prepared by known processes,some of the isocyanates of the formula VIII are novel and to this extentrepresent a further subject-matter of the invention.

The isocyanates of the formula VIII can be obtained, for example, byhydrolyzing a nitrile (of the formula A--CN) to an acid (of the formulaA--COOH) in a manner known per se and subsequently converting the latterinto the acid chloride (of the formula C--COCl) using a chlorinatingagent and then reacting the acid chloride with an azide, such as sodiumazide or trimethylsilyl azide, in an organic solvent, such as toluene.

Another possibility is to hydrogenate a nitrile (of the formula A--CN)to the amine (of the formula A--NH₂) and then to react this withphosgene.

The symbols A, X and R₂ are as defined above.

An example which may be mentioned of such isocyanates of the formulaVIII is 1-(2-isocyanatoethyl)-3-methylimidazolidine-2,4-dione.

The urethane-urethane-modified, crosslinkable polymers of the formula Xare obtained analogously by reacting a polyvinyl alcohol having amolecular weight of at least about 2000 which comprises units of theformula I

    --CH(OH)--CH.sub.2 --                                      (I)

and also acetate groups with from about 0.5 to 80%, based on the numberof hydroxyl groups in the polyvinyl alcohol, of an isocyanate of theformula VI

    CH.sub.2 ═CH--O--Z--O--CO--NH--Y--NCO                  (VI)

and an isocyanate of the formula VIII

    A--NCO                                                     (VIII)

in which the symbols Z, Y and A are as defined above, in a one-potprocess in an aprotic polar solvent at elevated temperature to give thecrosslinkable polymer of the formula X.

Suitable aprotic polar solvents are those mentioned above in connectionwith the preparation of the polymers of the formula V; the same appliesto the elevated temperature.

The novel crosslinkable polymers (prepolymers) comprising units offormulae XI and XII or XIII are water-soluble.

Surprisingly, the crosslinkable polymers comprising units of theformulae XI and XII or XIII are extremely stable. This is unexpected tothe person skilled in the art since higher-functional acrylates, forexample, usually require stabilization. If such compounds are notstabilized, rapid polymerization usually occurs. However, spontaneouscrosslinking due to homopolymerization does not occur with the novelcrosslinkable polymers. The crosslinkable polymers can, in addition, bepurified in a manner known per se, for example, as mentioned, byprecipitation with acetone, dialysis or ultrafiltration, particularpreference being given to ultrafiltration. This purification operationallows the crosslinkable polymers to be obtained in extremely pure form,for example as concentrated aqueous solutions, which are free or atleast substantially free from reaction products, such as salts, andstarting materials, or other non-polymeric constituents.

The preferred method for the purification of the novel crosslinkablepolymers, ultrafiltration, can be carried out in a manner known per se.It is possible to carry out the ultrafiltration repeatedly, for examplefrom two to ten times. Alternatively, the ultrafiltration can also becarried out continuously until the desired degree of purity has beenachieved. The desired degree of purity can in principle be as great asdesired. A suitable measure of the degree of purity is, for example, theNMR spectrum of the solution in DMSO or elemental analysis (N₂ content),gel permeation chromatography or HPLC.

In addition to the units of the formulae XI, XII or XIII, the novelwater-soluble, crosslinkable polymers can also comprise further modifierunits. Of the many possibilities for such modifiers, the following arementioned by way of example:

Further units containing crosslinkable groups are, for example, those ofthe formulae A and B ##STR24## in which R₁ and R₂ embody amino acidradicals and are, independently of one another: hydrogen, a C₁ -C₈ alkylgroup, an aryl group or a cyclohexyl group, these groups beingunsubstituted or monosubstituted or polysubstituted,

R₃ is hydrogen or a C₁ -C₄ alkyl group, and

R₄ is an --O-- or --NH-- bridge.

Further units containing crosslinkable groups are, for example, those ofthe formula C ##STR25## in which R is a linear or branched bivalentradical of a C₁ -C₁₂ alkane, preferably of a C₁ -C₆ alkane,

R₁ is hydrogen, a C₁ -C₆ alkyl group or a cycloalkyl group, preferably acyclohexyl group,

R₂ is hydrogen or a C₁ -C₆ alkyl group,

R₃ is the ##STR26## group if n=0, or the ##STR27## bridge if n=1, R₄ ishydrogen or C₁ -C₄ alkyl,

n is zero or 1, preferably 0, and

R₁₆ and R₁₇, independently of one another, are hydrogen, linear orbranched C₁ -C₈ alkyl, aryl, preferably phenyl, or cyclohexyl;

or those of the formula D ##STR28## in which R₁₅ is hydrogen or a C₁ -C₄alkyl group, in particular CH₃, and p is from zero to 6, preferably fromzero to 2, in particular zero.

Units which contain a bound photoinitiator are, in particular, those ofthe formula E ##STR29## in which BR is an ##STR30## bridge or aquaternary salt thereof which has the formula ##STR31##

PI is the radical of a photoinitiator from the class consisting of thebenzoins, such as benzoin ethers, for example benzoin methyl ether,benzoin ethyl ether, benzoin isopropyl ether and benzoin phenyl ether,and benzoin acetate; acetophenones, such as acetophenone,2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone; benzil, benzilketals, such as benzil dimethyl ketal and benzil diethyl ketal;anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tert-butyl anthraquinone, 1-chloroanthraquinone and2-amylanthraquinone; furthermore benzophenones, such as benzophenone and4,4'-bis(N,N'-dimethylamino)benzophenone; thioxanthones and xanthones;acridine derivatives; phenazine derivatives; quinoxaline derivatives;and 1-aminophenyl ketones and in particular 1-hydroxyphenyl ketones, inparticular those of the formula ##STR32## in which X is --O--, --S-- or--N(R₁₂)--,

Y is a counterion, such as H₂ SO₄.sup.⊖, F.sup.⊖, Cl.sup.⊖, Br.sup.⊖,I.sup.⊖, CH₃ COO.sup.⊖, OH.sup.⊖, BF₄.sup.⊖ or

H₂ PO₄.sup.⊖,

R₃ is hydrogen, a C₁ -C₆ alkyl group or a cycloalkyl group,

R₇ is hydrogen; unsubstituted or substituted, linear or branched C₁ -C₁₂alkyl; the --(CH₂)_(r) --PI group or the --CO--R₁₃ group, in which R₁₃is linear or branched C₁ -C₆ alkyl which is unsubstituted or substitutedby --COOH or acrylamide, or an unsubstituted, linear or branched radicalof a C₃ -C₈ olefin,

R₈ is hydrogen, or unsubstituted or substituted, linear or branched C₁-C₄ alkyl so long as R₇ is not --CO--R₁₃,

R₉ is unsubstituted or substituted, linear or branched C₁ -C₆ alkyl,unsubstituted or substituted, linear or branched C₁ -C₆ alkoxy, a6-membered carbocyclic or heterocyclic ring, or an unsubstituted linearor branched radical of a C₃ -C₈ olefin,

R₁₀ is a group of the formula --OR₁₄ or ##STR33## R₁₁ is unsubstitutedor substituted, linear or branched C₁ -C₆ alkyl, a 6-memberedcarbocyclic or heterocyclic ring, an unsubstituted, linear or branchedradical of a C₃ -C₈ olefin, or aryl, where

R₉ and R₁₁ together can also be cyclized to form a 5- or 6-memberedcarbocyclic ring,

R₁₂ is hydrogen or unsubstituted, linear or branched C₁ -C₄ alkyl,

R₁₄ is hydrogen or unsubstituted or substituted, linear or branched C₁-C₄ alkyl,

R₁₅ and R₁₆, independently of one another, are unsubstituted, linear orbranched C₁ -C₄ alkyl, or R₁₅ and R₁₆ can be bonded together to form a5- or 6-membered heterocyclic ring,

m is 0 or 1,

n is a number from 1 to 12,

o is a number from 1 to 6, and

r is a number from 2 to 6,

where substituted radicals are substituted, in particular, by C₁ -C₄alkyl or by C₁ C₄ alkoxy, with the following provisos:

if the BR bridge is a quaternary salt, n is a number from 2 to 12;

R₁₄ is not hydrogen if R₉ is a C₁ -C₆ alkoxy radical; and

R₇ is --CO--R₁₃ when n=1.

Examples of units containing basic groups are those of the formula F##STR34## in which R is a linear or branched bivalent radical of a C₁-C₁₂ alkane, and R₃ is hydrogen, a C₁ -C₆ alkyl group or a cycloalkylgroup, and R₇ is a basic primary, secondary or tertiary amino group, inparticular a secondary or tertiary amino group which is substituted byC₁ -C₆ alkyl, or a quaternary amino group of the formula

    --N⊕(R').sub.3 X⊖

in which R' is hydrogen or, independently of one another, a C₁ -C₁₂alkyl radical, in particular a C₁ -C₄ alkyl radical, and X is acounterion, for example HSO₄.sup.⊖, F.sup.⊖, Cl.sup.⊖, Br.sup.⊖,I.sup.⊖, CH₃ COO.sup.⊖, OH.sup.⊖, BF.sup.⊖ or H₂ PO₄.sup.⊖.

Examples of units containing acidic groups are those of the formula G##STR35## in which R and R₃ are as defined under the formula F, and R₈is the radical of a monobasic, dibasic or tribasic aliphatic oraromatic, saturated or unsaturated organic acid.

Examples of units containing a covalently bonded reactive dye radicalare those of the formula H, I, J or K ##STR36## in which RF' is aradical of the formula ##STR37## in which D is the radical of an organicdye,

R₁₄ is a divalent electron-withdrawing group,

U is hydrogen or halogen,

R is the divalent radical of a C₁ -C₁₂ alkane,

R₁ is hydrogen or C₁ -C₄ alkyl,

R₃ is hydrogen, C₁ -C₆ alkyl or cycloalkyl, and

Y is --O-- or --N(R₁)--.

The novel crosslinkable polymers can be crosslinked in an extremelyeffective and targeted manner, in particular by photochemicalcrosslinking.

The present invention therefore furthermore relates to aphotocrosslinked polymer which can be obtained by photocrosslinking acrosslinkable polymer comprising units of the formulae XI and XII orXIII in the presence or absence of an additional vinylic comonomer.These photocrosslinked polymers are three-dimensional polymeric networksthrough the formation of covalent and non covalent (for examplecoordinative, ionic, etc.) bonds and are insoluble, but swellable, inwater.

In the case of photochemical crosslinking (photocrosslinking), it isexpedient to add a photoinitiator which is capable of initiatingfree-radical crosslinking. The crosslinking can then be initiated byactinic or ionizing radiation.

The photocrosslinking is carried out in a suitable solvent. Suchsolvents are in principle all those which dissolve the polyvinyl alcoholand any vinylic comonomers additionally used.

The photocrosslinking is preferably carried out from an aqueous solutionof the novel crosslinkable polymers, which can be obtained as a resultof the preferred purification step, namely ultrafiltration, if desiredafter addition of an additional vinylic comonomer.

The vinylic comonomer which can additionally be used in accordance withthe invention in the photocrosslinking can be hydrophilic, hydrophobicor a mixture of hydrophobic and hydrophilic vinylic monomers. Suitablevinylic monomers include, in particular, those which are usually used inthe production of contact lenses. The term "hydrophilic vinylic monomer"is taken to mean a monomer which, as a homopolymer, typically gives apolymer which is soluble in water or is capable of absorbing at least10% by weight of water. Analogously, the term "hydrophobic vinylicmonomer" is taken to mean a monomer which, as a homopolymer, typicallygives a polymer which is insoluble in water or is capable of absorbingless than 10 per cent by weight of water.

In general, from about 0.01 to 80 units of a typical vinylic comonomerreact per unit of formula XI.

If a vinylic comonomer is used, the photocrosslinked novel polymerspreferably comprise from about 1 to 15 per cent, particularly preferablyfrom about 3 to 8 per cent, of units of the formulae XI and XII or XIII,based, for example, on the number of hydroxyl groups in the polyvinylalcohol, which are reacted with from about 0.1 to 80 units of thevinylic monomer.

The proportion of vinylic comonomers, if used, is preferably from 0.5 to80 units per unit of the formulae XI and XII or XIII, in particular from1 to 30 units of vinylic comonomer per unit of the formulae XI and XIIor XIII, particularly preferably from 5 to 20 units per unit of theformulae XI and XII or XIII.

It is furthermore preferred to use a hydrophobic vinylic comonomer or amixture of a hydrophobic vinylic comonomer and a hydrophilic vinyliccomonomer which comprises at least 50 per cent by weight of ahydrophobic vinylic comonomer. This allows the mechanical properties ofthe photocrosslinked polymer to be improved without drastically reducingthe water content. However, both conventional hydrophobic vinyliccomonomers and conventional hydrophilic vinylic comonomers are inprinciple suitable for the copolymerization with polyvinyl alcoholcontaining groups of the formulae XI and XII or XIII.

Suitable hydrophobic vinylic comonomers include, without this being acomprehensive list, C₁ -C₁₈ alkyl acrylates and methacrylates, C₃ -C₁₈alkylacrylamides and -methacrylamides, acrylonitrile, methacrylonitrile,vinyl C₁ -C₁₈ alkanoates, C₂ -C₁₈ alkenes, C₂ -C₁₈ haloalkenes, styrene,C₁ -C₆ alkylstyrene, vinyl alkyl ethers in which the alkyl moiety has 1to 6 carbon atoms, C₂ -C₁₀ operfluoroalkyl acrylates and methacrylatesand correspondingly partially fluorinated acrylates and methacrylates,C₃ -C₁₂ perfluoroalkyl ethylthiocarbonylaminoethyl acrylates and-methacrylates, acryloxy- and methacryloxyalkylsiloxanes,N-vinylcarbazole, C₁ -C₁₂ alkyl esters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given to, forexample, C₁ -C₄ alkyl esters of vinylically unsaturated carboxylic acidshaving 3 to 5 carbon atoms or vinyl esters of carboxylic acids having upto 5 carbon atoms.

Examples of suitable hydrophobic vinylic comonomers include methylacrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethylmethacrylate, propyl methacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyltoluene, vinyl ethyl ether,perfluorohexylethylthiocarbonylaminoethyl methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoroisopropylmethacrylate, hexafluorobutyl methacrylate,tris(trimethylsilyloxy)silylpropyl methacrylate,3-methacryloxypropyl-pentamethyldisiloxane andbis(methacryloxypropyl)tetramethyldisiloxane.

Suitable hydrophilic vinylic comonomers include, without this being acomprehensive list, hydroxy-substituted lower alkyl acrylates andmethacrylates, acrylamide, methacrylamide, lower alkylacrylamides and-methacrylamides, methoxylated acrylates and methacrylates,hydroxy-substituted lower alkylacrylamides and -methacrylamides,hydroxy-substituted lower alkyl vinyl ethers, sodium ethylenesulfonate,sodium styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid,N-vinylpyrrole, N-vinylsuccinimide, N-vinylpyrrolidone, 2- and4-vinylpyridine, acrylic acid, methacrylic acid, amino- (where the term"amino" also covers quaternary ammonium), mono(lower alkyl)amino- ordi(lower alkyl)amino(lower alkyl) acrylates and methacrylates allylalcohol and the like. Preference is given to, for example,hydroxy-substituted C₂ -C₄ alkyl (meth)acrylates, five-to seven-memberedN-vinyllactams, N,N-di-C₁ -C₄ alkyl(meth)acrylamides and vinylicallyunsaturated carboxylic acids having a total of 3 to 5 carbon atoms.

Examples of suitable hydrophilic vinylic comonomers include hydroxyethylmethacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide,dimethylacrylamide, allyl alcohol, vinylpyridine, vinylpyrrolidone,glycerol methacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide and thelike.

Preferred hydrophobic vinylic comonomers are methyl methacrylate andvinyl acetate.

Preferred hydrophilic vinylic comonomers are 2-hydroxyethylmethacrylate, N-vinylpyrrolidone and acrylamide.

However, suitable comonomers also include the crosslinkable polymerscomprising units of the formulae XI and XII or XIII themselves, it beingpossible, for example, for a crosslinkable polymer of formula V to becompolymerized, for example with a crosslinkable polymer of the formulaIX, and also terpolymerized, for example also with a crosslinkablepolymer of the formula VII.

The novel crosslinkable polymers can be converted into mouldings, inparticular contact lenses, in a manner known per se, for example bycarrying out the photocrosslinking of novel crosslinkable polymers in asuitable contact-lens mould. The invention therefore furthermore relatesto mouldings essentially comprising a novel crosslinkable polymercomprising units of the formulae XI and XII or XIII. Further examples ofnovel mouldings, besides contact lenses, are biomedical mouldings andmouldings for specifically ophthalmic purposes, for example intraocularlenses, eye bandages, mouldings which can be used in surgery, such asheart valves, artificial arteries or the like, furthermore films andmembranes, for example membranes for diffusion control,photostructurable films for information storage, and photoresistmaterials, for example membranes and mouldings for etch resists andscreen printing resists.

A specific embodiment of the invention relates to contact lenses whichcomprise a novel crosslinked polymer made from a crosslinkable polymercomprising units of the formulae XI and XII or XIII or essentiallycomprise or consist of a novel crosslinked polymer. Contact lenses ofthis type have a range of unusual and extremely advantageous properties,including, for example, excellent compatibility with the human cornea,based on a balanced ratio between water content (about 50-90% by weight,in particular 60-85% by weight), high oxygen permeability and very goodmechanical properties, for example transparency, clarity, freedom fromstresses and tear strength. In addition, the novel contact lenses havehigh dimensional stability. Even after autoclaving one or more times at,for example, about 120° C. for about 30-40 minutes, no changes in shapeare observed.

It is furthermore emphasized that the novel contact lenses, ie. thosecomprising a crosslinked polymer made from a crosslinkable polymercomprising units of the formulae XI and XII or XIII can be produced verysimply and efficiently compared with the prior art. This is due to anumber of factors. Firstly, the starting materials, such as thepolyvinyl alcohol, are inexpensive to obtain or prepare. Secondly, it isadvantageous that the crosslinkable polymers are surprisingly stable, sothat they can be subjected to very substantial purification. Thecrosslinking can therefore be carried out using a crosslinkable polymerwhich requires virtually no subsequent purification, such as, inparticular, complex extraction of unpolymerized constituents.Furthermore, the crosslinking can be carried out in purely aqueoussolution, so that a subsequent hydration step is unnecessary. Finally,the photocrosslinking takes place within about 5-20 seconds, so that theprocess for the production of the novel contact lenses can be designedto be extremely economical from this point of view too.

All the above advantages naturally apply not only to contact lenses, butalso to the other mouldings mentioned. The totality of the variousadvantageous aspects in the production of novel mouldings results innovel mouldings being particularly suitable as mass-produced articles,for example as contact lenses, which are also worn for a short time span(from about 1 to 14 days, preferably from about 1 to 4 days) and arethen replaced by new lenses.

The present invention furthermore relates to the production of the novelmouldings, in particular the novel contact lenses. These processes areillustrated below using the example of contact lenses. However, theseprocesses can also be used for the other mouldings mentioned.

The novel contact lenses can be produced in a manner known per se, forexample in a conventional spin-casting mould, as described, for example,in U.S. Pat. No. 3,408,429, or by the full-mould process in a staticmould, as described, for example, in U.S. Pat. No. 4,347,198.

It has been observed in accordance with the invention that the processdescribed above with reference to crosslinkable PVA polymers is ofgeneral applicability. The present invention therefore also relates to anovel process for the production of polymeric mouldings, in particularcontact lenses, in which a water-soluble crosslinkable polymercomprising crosslinkable units of the formulae XI and XII, XI and XIIIor XI, XII and XIII is crosslinked in solution, and to mouldings, inparticular contact lenses, obtainable by this process.

In detail, this process for the production of mouldings, in particularcontact lenses, comprises the following steps:

a) preparation of an essentially aqueous solution of a water-solublecrosslinkable polymer comprising crosslinkable units of the formula XI##STR38## and at least one further modifier comprising units of theformula XII ##STR39## or units of the formula XIII ##STR40## in which Uis an ##STR41## or --Y--NH--CO--O--Z--O--CH═CH₂ group, X is a bridgehaving 2 to 12 carbon atoms,

R₂ is hydrogen or a C₂ -C₄ alkyl group,

Y is a bridge having 7 to 12 carbon atoms,

Z is a C₂ -C₁₂ alkylene bridge, which may be interrupted once or morethan once by an oxygen atom,

R₃ is hydrogen, a C₁ -C₆ alkyl group or a cycloalkyl group,

R is a C₁ -C₁₂ alkylene bridge,

R₁ is an organic group having 1 to 18 carbon atoms,

A is an organic radical having 1 to 18 carbon atoms, and

m is 0 or 1,

b) introduction of the resultant solution into a mould,

c) initiation of the crosslinking in water or in an organic solvent inwhich the crosslinkable polymer is dissolved, and

d) opening of the mould so that the moulding can be removed.

Unless expressly excluded below, the comments and preferences givenabove in connection with the crosslinkable PVA polymers comprising unitsof the formulae XI and XIII or XIII and the comments and preferencesgiven in connection with the processes for the preparation of polymersand production of mouldings, in particular contact lenses, from thesecrosslinkable polymers also apply in connection with the above-describedprocess comprising steps a), b), c) and d). This applies to all cases inwhich the comments and preferences in connection with crosslinkable PVApolymers comprising units of the formulae XI, XII or XIII can be appliedappropriately to the process described above.

The crucial criteria regarding whether a crosslinkable polymer can beemployed in the novel process are that the crosslinkable polymer issoluble in water and comprises units of the formulae XI and XII or XIII.

An essentially aqueous solution of a novel crosslinkable polymer can beprepared in a manner known per se, for example by isolating thecrosslinkable polymer, for example in pure form, ie. free from undesiredconstituents, and dissolving the crosslinkable polymer in an essentiallyaqueous medium.

The criterion that the crosslinkable polymer is soluble in water is, forthe purposes of the invention, taken to mean in particular that thecrosslinkable polymer is soluble in an essentially aqueous solution at20° C. in a concentration of from about 3 to 90 per cent by weight,preferably from about 5 to 60 per cent by weight, in particular fromabout 10 to 60 per cent by weight. If possible in individual cases,crosslinkable polymer concentrations of greater than 90% are alsoincluded for the purposes of the invention. Particular preference isgiven to crosslinkable polymer concentrations in solution of from about15 to about 50 per cent by weight, in particular from about 15 to about40 per cent by weight, for example from about 20 to about 40 per cent byweight.

For the purposes of this invention, essentially aqueous solutions of thecrosslinkable polymer include in particular solutions of thecrosslinkable polymer in water, in aqueous salt solutions, in particularin aqueous salt solutions having an osmolarity of from about 200 to 450milliosmol in 1000 ml (unit: mOsm/l), preferably an osmolarity of fromabout 250 to 350 mOsm/l, in particular about 300 mOsm/l, or in mixturesof water or aqueous salt solutions with physiologically acceptable polarorganic solvents, for example glycerol. Preference is given to solutionsof the crosslinkable polymers in water alone.

The aqueous salt solutions are advantageously solutions ofphysiologically acceptable salts, such as buffer salts, for examplephosphate salts, which are conventional in the area of contact-lenscare, or isotonicizing agents, in particular alkali metal halides, forexample sodium chloride, which are conventional in the area ofcontact-lens care, or solutions of mixtures thereof. An example of aparticularly suitable salt solution is an artificial, preferablybuffered tear fluid whose pH and osmolarity have been matched to naturaltear fluid, for example an unbuffered, preferably buffered for exampleby phosphate buffer, sodium chloride solution whose osmolarity and pHconform to the osmolarity and pH of human tear fluid.

The above-defined, essentially aqueous solutions of the crosslinkablepolymer are preferably pure solutions, ie. those which are free oressentially free from undesired constituents. Particular preference isgiven to solutions of the crosslinkable polymer in pure water or in anartificial tear fluid as described above.

The viscosity of the solution of the crosslinkable polymer in theessentially aqueous solution is unimportant over broad limits. However,it should preferably be a flowable solution which can be shaped withoutstresses.

The mean molecular weight of the crosslinkable polymer is likewiseunimportant within broad limits. However, the crosslinkable polymerpreferably has a molecular weight of from about 10,000 to about 200,000.

Suitable polymeric backbones, in addition to polyvinyl alcohol (PVA),are materials as have in some cases already been proposed ascontact-lens materials, for example polymeric diols other than PVA,polymers comprising saccharides, polymers comprising vinylpyrrolidone,polymers comprising alkyl (meth)acrylates, polymers comprising alkyl(meth)acrylates which are substituted by hydrophilic groups, such ashydroxyl, carboxyl or amino groups, polyalkylene glycols, or copolymersor mixtures thereof.

The crosslinkable polymer (prepolymer) used in accordance with theinvention comprises the units containing one or more differentcrosslinkable group(s) and, if desired, the units containing the furthermodifier(s), reactive dye radicals and photoinitiator radicals, etc, ina total amount of from about 0.5 to 80%, preferably from 1 to 50%,advantageously from 1 to 25%, in particular from 2 to 15%, particularlypreferably from 2 to 10%, based on the number of functional groups inthe starting polymer, for example hydroxyl groups in the polyvinylalcohol.

Crosslinkable polymers (prepolymers) which can be crosslinked inaccordance with the invention and are intended for the production ofcontact lenses comprise, in particular, from about 0.5 to about 25%,especially from about 1 to 15%, particularly preferably from about 2 to12%, of these units.

As already mentioned, for a crosslinkable polymer to be suitable in thenovel process, it is essential that it is a crosslinkable polymer.However, the crosslinkable polymer is uncrosslinked or at leastessentially uncrosslinked so that it is water-soluble.

Furthermore, the crosslinkable polymer is advantageously stable in theuncrosslinked state, so that it can be subjected to purification, asdescribed above in connection with compounds comprising units of theformulae XI and XIII or XIII. The crosslinkable polymers are preferablyemployed in the novel process in the form of pure solutions. Thecrosslinkable polymers can be converted into the form of pure solutionsas described below, for example.

The crosslinkable polymers used in the novel process can preferably bepurified in a manner known per se, for example by precipitation withorganic solvents, such as acetone, filtration and washing, extraction ina suitable solvent, dialysis or ultrafiltration, particular preferencebeing given to ultrafiltration. This purification operation allows thecrosslinkable polymers to be obtained in extremely pure form, forexample as concentrated aqueous solutions, which are referred tohereinafter as pure or essentially pure. This term is understood torefer to a crosslinkable polymer or to a solution thereof which is freeor at least substantially free from undesired constituents.

Undesired constituents in this context are generally all constituentswhich are physiologically undesired, especially monomeric, oligomeric orpolymeric starting compounds used for the preparation of thewater-soluble, crosslinkable polymer, or byproducts formed during thepreparation of the water-soluble, crosslinkable polymer. Preferreddegrees of purity of these constituents are less than 0.01%, inparticular less than 0.001%, very particularly preferably less than0.0001% (1 ppm). It is to be noted, however, that there may be presentin the solution, for example by formation as byproducts during thepreparation of the water-soluble, crosslinkable polymer, constituentswhich are not undesired from a physiological point of view, such as forexample sodium chloride. Preferred degrees of purity of theseconstituents are less than 1%, in particular less than 0.1%, veryparticularly preferably less than 0.01%. In most cases such levels ofconstituents may be obtained by applying 3 to 4 repeated ultrafiltrationcycles.

The preferred process for the purification of the crosslinkable polymersused in the novel process, namely ultrafiltration, can be carried out ina manner known per se. The ultrafiltration can be carried outrepeatedly, for example from two to ten times. Alternatively, theultrafiltration can also be carried out continuously until the desireddegree of purity has been achieved. The desired degree of purity can inprinciple be chosen to be as great as desired.

In a preferred embodiment of the novel process, an essentially aqueoussolution of the crosslinkable polymer which is essentially free fromundesired constituents, for example free from monomeric, oligomeric orpolymeric starting compounds used for the preparation of thecrosslinkable polymer, and/or free from by-products formed during thepreparation of the crosslinkable polymer, is prepared in step a) andused further. This essentially aqueous solution is particularlypreferably a purely aqueous solution or a solution in an artificial tearfluid as described above. It is furthermore preferred for the novelprocess to be carried out without addition of a comonomer, for example avinylic comonomer.

Owing to the abovementioned measures and in particular owing to acombination of said measures, the novel process is carried out using asolution of the crosslinkable polymer containing no or essentially noundesired constituents requiring extraction after crosslinking. It istherefore a particular feature of this preferred embodiment of the novelprocess that extraction of undesired constituents is not necessary afterthe crosslinking.

The novel process is therefore preferably carried out in such a way thatthe essentially aqueous solution of the crosslinkable polymer is free oressentially free from undesired constituents, in particular frommonomeric, oligomeric or polymeric starting compounds used for thepreparation of the crosslinkable polymer, or from by-products formedduring the preparation of the crosslinkable polymer, and/or that thesolution is used without addition of a comonomer.

An addition which may be added to the solution of the crosslinkablepolymer is a photoinitiator for the crosslinking so long as an initiatoris necessary for crosslinking of the crosslinkable groups. This may bethe case, in particular, if the crosslinking takes place byphotocrosslinking, which is preferred in the novel process.

In the case of photocrosslinking, it is expedient to add an initiatorwhich is capable of initiating free-radical crosslinking and is readilysoluble in water. Examples thereof are known to the person skilled inthe art; suitable photoinitiators which may be mentioned specificallyare benzoins, such as benzoin, benzoin ethers, such as benzoin methylether, benzoin ethyl ether, benzoin isopropyl ether and benzoin phenylether, and benzoin acetate; acetophenones, such as acetophenone,2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone; benzil, benzilketals, such as benzil dimethyl ketal and benzil diethyl ketal,anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tert-butylanthraquinone, 1-chloroanthraquinone and2-amylanthraquinone; furthermore triphenylphosphine, benzoylphosphineoxides, for example 2,4,6-trimethylbenzoyl-diphenylphosphine oxide,benzophenones, such as benzophenone and 4,4'-bis(N,N'-dimethylamino)benzophenone; thioxanthones and xanthones; acridinederivatives; phenazine derivatives; quinoxaline derivatives and1-phenyl-1,2-propanedione 2-O-benzoyl oxime; 1-aminophenyl ketones and1-hydroxyphenyl ketones, such as 1-hydroxycyclohexylphenyl ketone,phenyl 1-hydroxyisopropyl ketone, 4-isopropylphenyl 1-hydroxyisopropylketone, 2-hydroxy-1- 4-(2-hydroxyethoxy)phenyl!-2-methylpropan-1-one,1-phenyl-2-hydroxy-2-methylpropan-1-one, and2,2-dimethoxy-1,2-diphenylethanone, all of which are known compounds.

Particularly suitable photoinitiators, which are usually used incombination with UV lamps as light source, are acetophenones, such as2,2-dialkoxybenzophenones and hydroxyphenyl ketones, for example2-hydroxy-1- 4-(2-hydroxyethoxy)phenyl!-2-methylpropan-1-one and1-phenyl-2-hydroxy-2-methylpropan-1-one.

Another class of photoinitiators usually employed when argon ion lasersare used are benzil ketals, for example benzil dimethyl ketal.

The initiator used is preferably the initiator known under the nameIRGACURE® 2959.

The photoinitiators are added in effective amounts, expediently inamounts of from about 0.1-2% by weight, in particular from 0.3 to 0.5%by weight, based on the total amount of the crosslinkable polymer.

The resultant solution can be introduced into a mould using methodsknown per se, such as, in particular, conventional metering, for exampledropwise. The novel contact lenses can be produced in a manner known perse, for example in a conventional spin-casting mould, as described, forexample, in U.S. Pat. No. 3,408,429, or by the full-mould process in astatic mould, as described, for example, in U.S. Pat. No. 4,347,198.Appropriate moulds are made, for example, of polypropylene. Examples ofsuitable materials for reusable moulds are quartz and sapphire glass.

The crosslinkable polymers which are suitable in accordance with theinvention can be crosslinked by irradiation with ionizing or actinicradiation, for example electron beams, X-rays, UV or VIS light, ie.electromagnetic radiation or particle radiation having a wavelength inthe range from about 280 to 650 nm. He/Cd, argon ion or nitrogen ormetal vapour or NdYAG laser beams with multiplied frequency areparticularly suitable. It is known to the person skilled in the art thateach selected light source requires selection and, if necessary,sensitization of the suitable photoinitiator. It has been recognizedthat in most cases the depth of penetration of the radiation into thecrosslinkable polymer and the rate are in direct correlation with theabsorption coefficient and concentration of the photoinitiator.

The crosslinking can also be initiated thermally if desired.

It should be emphasized that the crosslinking can take place in a veryshort time in accordance with the invention, for example in less thanfive minutes, preferably in less than one minute, in particular in up to30 seconds, even in 3-30 seconds.

Apart from water, which is preferred, the crosslinking medium canadditionally be any medium in which the crosslinkable polymer issoluble. In the case of polyvinyl alcohol as the polymer backbone, allsolvents which dissolve polyvinyl alcohol are suitable, such asalcohols, for example ethanol, glycols, glycerol, piperazine (atelevated temperature), diamines, such as triethylenediamine, formamide,dimethylformamide, hexamethylphosphoric triamide, dimethyl sulfoxide,pyridine, nitromethane, acetonitrile, nitrobenzene, chlorobenzene,trichloromethane, dioxane and aqueous solutions of tetraalkylammoniumbromide and iodide.

The opening of the mould so that the moulding can be removed can becarried out in a manner known per se. Whereas the process proposed inthe prior art (U.S. Pat. No. 3,408,429 and 4,347,198) requiressubsequent purification steps at this point, for example by extraction,and also steps for hydration of the resultant mouldings, in particularcontact lenses, such steps are unnecessary in the novel process.

Since the solution of the crosslinkable polymer preferably comprises noundesired low-molecular-weight constituents, the crosslinked productalso comprises no such constituents. Subsequent extraction is thereforeunnecessary. Since the crosslinking is carried out in an essentiallyaqueous solution, subsequent hydration is unnecessary. These twoadvantages mean, inter alia, that complex subsequent treatment of theresultant mouldings, in particular contact lenses, is unnecessary. Thecontact lenses obtainable by the novel process are thereforedistinguished, in an advantageous embodiment, by the fact that they aresuitable for their intended use without extraction. The term `intendeduse` in this connection is taken to mean, in particular, that thecontact lenses can be employed in the human eye. The contact lensesobtainable by the novel process are furthermore distinguished in anadvantageous embodiment by the fact that they are suitable for theirintended use without hydration.

The novel process therefore proves to be extremely suitable for theefficient production of a large number of mouldings, such as contactlenses, in a short time. The contact lenses obtainable by this processhave, inter alia, the advantages over the contact lenses known from theprior art that they can be used as intended without subsequent treatmentsteps, such as extraction or hydration.

The examples below serve to further illustrate the invention. In theexamples, unless expressly stated otherwise, amounts are by weight andtemperatures are given in degrees Celsius. Examples are not intended torepresent any restriction of the invention, for example to the scope ofthe examples.

EXAMPLE 1

263.0 g (1.622 mol) of 1,1'-carbonyldiimidazole and 1.5 l oftetrahydrofuran are introduced into a 2.5 l glass apparatus which hasbeen flushed with nitrogen gas and is fitted with stirrer, thermometer,reflux condenser and dropping funnel. 250.0 g (1.59 mol) of3-(2-oxopyrrolidin-1-yl)propionic acid are introduced in portions intothis suspension with stirring over the course of 10 minutes at aninternal temperature of 19°-24° C., the carbon dioxide gas formed beingdischarged via the condenser. The reaction temperature is then raised to38° C. over the course of 20 minutes, and 170.5 g (1.622 mol) of2-aminoacetaldehyde dimethyl acetal are added dropwise over the courseof 20 minutes at a reaction temperature of 38°-53° C. The reaction isallowed to continue at the boiling point for a further 1 hour and 35minutes, the solvent is distilled off in a rotary evaporator, and theresidue is dried at 110° C./0.1 mbar. The residue is dissolved in 400 mlof toluene, the solution is cooled to -25° C., the imidazole whichcrystallizes out is removed by filtration, the filtrate is evaporated ina rotary evaporator, and the residue is dried at 120° C./0.1 mmHg. Thecrude product is dissolved in 400 ml of a mixture of methylene chloride,ethanol and triethylamine (ratio 90:9:1) and purified over achromatography column packed with 3.5 kg of silica gel 60 from E. Merck.The appropriate fractions are combined, and the solution is evaporatedat 80° C. in a rotary evaporator, and the resultant product is dried at90° C./0.1 mbar, giving 356.8 g (91.8% of theory) of a liquidN-(2,2-dimethoxyethyl)-3-(2-oxopyrrolidin-1-yl)propionamide having thefollowing analytical data:

Elemental analysis:

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            54.08    53.89                                                 % H            8.25     8.31                                                  % N            11.47    11.53                                                 ______________________________________                                    

Acetal content: 24.2% of OCH₃ (theory: 25.4%)

Structure: ##STR42##

EXAMPLE 2

Analogously to Example 1, 165.43 g (1.02 mol) of1,1'-carbonyldiimidazole and 700 ml of tetrahydrofuran are introducedinto an apparatus, allowed to react with 202.86 g (1.0 mol) of3-(4,4-dimethyl-2,5-dioxoimidazolidin-1-yl)propionic acid andsubsequently reacted with 107.21 g (1.02 mol) of 2-aminoacetaldehydedimethyl acetal. The reaction mixture is evaporated to dryness at 80°C./0.1 mbar in a rotary evaporator, and the resultant residue ispurified analogously to Example 1, giving 154.2 g (54.2% of theory) ofN-(2,2-dimethoxyethyl)-3-(4,4-dimethyl-2,5-dioxoimidazolidin-1-yl)propionamide,which melts at 123° C.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            50.16    50.43                                                 % H            7.37     7.40                                                  % N            14.43    14.61                                                 ______________________________________                                    

Acetal content: 21.22% of OCH₃ (theory: 21.60%)

Structure: ##STR43##

EXAMPLE 3

82.7 g (0.51 mol) of 1,1'-carbonyldiimidazole in 5.0 l oftetrahydrofuran are allowed to react as described in Example 1, with93.08 g (0.5 mol) of3-(3,5,5-trimethyl-2,4-dioxoimidazolidin-1-yl)propionic acid and aresubsequently reacted with 53.62 g (0.51 mol) of 2-aminoacetaldehydedimethyl acetal. The reaction mixture is evaporated in a rotaryevaporator, and the imidazole present in the residue is removed bydistillation at a bath temperature of 120° C./0.1 mmHg for 3 hours,giving 134.1 g (98.1% of theory) of a brownish, liquid crude product,which is recrystallized from 130 ml of ethyl acetate, giving 88.1 g(65.0% of theory) of colourless, crystalline N-(2,2-dimethoxyethyl)-3-(3,5,5-trimethyl-2,4-dioxoimidazolidin-1-yl)propionamide,whose melting point is 86.4° C.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            48.34    48.61                                                 % H            7.01     7.08                                                  % N            15.38    15.65                                                 ______________________________________                                    

Acetal content: 21.69% of OCH₃ (theory: 22.71%)

Structure: ##STR44##

EXAMPLE 4

85.46 g (0.667 mol) of 5,5-dimethylhydantoin, 110.6 g (0.80 mol) ofanhydrous potassium carbonate and 124.0 g (0.7336 mol) of2-bromoacetaldehyde dimethyl acetal in 600 ml of dimethylformamide arereacted for about 6 hours analogously to Example 1 in a glass apparatus.The reaction mixture is subsequently cooled to room temperature andfiltered with suction, the filtrate is evaporated in a rotaryevaporator, and the residue is dried at 110° C./0.1 mbar. The crudeyield is 143.2 g (99.3% of theory) of3-(2,2-dimethoxyethyl)-5,5-dimethylimidazolidine-2,4-dione. 21 g of thecrude product are dissolved in 50 ml of 0.1N sodium hydroxide solutionat room temperature, and the solution is extracted 3 times by shakingwith 30 ml of tert-butyl methyl ether in each case in a separatingfunnel. The organic phases are combined, the solution is dried usinganhydrous sodium sulfate and subsequently filtered, the clear filtrateis evaporated in a rotary evaporator, and the residue is dried for 1hour at 60° C./0.1 mbar, giving 12.3 g of pure, highly viscous3-(2,2-dimethoxyethyl)-5,5-dimethylimidazolidine-2,4-dione having thefollowing analytical data:

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            44.99    50.17                                                 % H            7.46     7.44                                                  % N            12.96    13.00                                                 ______________________________________                                    

Structure: ##STR45##

EXAMPLE 5

87.0 g (0.762 mol) of 1-methylhydantoin and 48.55 g (0.915 mol) ofacrylonitrile are introduced into an apparatus at an internaltemperature of 67° C., and 8 ml of 1 molar sodium hydroxide solution areadded dropwise over the course of 12 minutes, during which an exothermicreaction occurs and the temperature rises to 75° C. The reaction mixtureis then stirred for 1 hour and 48 minutes at 75° C.-103° C. and thenneutralized with 0.92 g of 32% hydrochloric acid. The reaction productis purified by vacuum distillation, giving 94.7 g (74.3% of theory) ofcrystalline 3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionitrile, whosemelting point is 53° C.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            50.29    50.21                                                 % H            5.43     5.49                                                  % N            25.14    25.04                                                 ______________________________________                                    

Structure: ##STR46##

EXAMPLE 6

334.33 g (2.0 mol) of3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionitrile, prepared asdescribed in Example 5, are hydrolysed for 5 hours and 30 minutes at96°-107° C. in a mixture of 1482.7 g (13.0 mol) of aqueous 32%hydrochloric acid and 288.3 g (4.8 mol) of acetic acid. The reactionsolution is then evaporated at 90° C. under reduced pressure in a rotaryevaporator and dried at 120° C./0.1 mbar to constant weight, giving354.1 g (95.1% of theory) of crude product, which is purified byrecrystallization from 1 liter of ethyl acetate, giving 184 g (50.4% oftheory) of crystalline 3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionicacid having a melting point of 109° C.

Elemental analysis

    ______________________________________                                                    calculated                                                                           found                                                      ______________________________________                                        % C           45.16    45.43                                                  % H           5.41     5.454                                                  % N           15.05    14.80                                                   ##STR47##                                                                    ______________________________________                                    

EXAMPLE 7

340.9 g (2.6857 mol) of oxalyl chloride are added dropwise over thecourse of 18 minutes at an internal temperature of 19°-23° C. to asolution of 100.0 g (0.537 mol) of3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionic acid, synthesized asdescribed in Example 6, 350 ml of methylene chloride and 1 ml ofdimethyl formamide, and the mixture is subsequently stirred at roomtemperature for 5 hours and 10 minutes. When the reaction is complete,the reaction mixture is evaporated in a rotary evaporator, the residueis stripped 3 times at 50° C. under reduced pressure with 100 ml oftoluene in each case, and the residue is dried at 60° C./0.1 mbar toconstant weight, giving 106.1 g (97.3% of theory) of solid, brownish3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionyl chloride having thefollowing analytical data:

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            41.09    41.44                                                 % H            4.43     4.51                                                  % N            13.69    13.58                                                 % Cl           17.33    16.96                                                 ______________________________________                                    

Structure: ##STR48##

EXAMPLE 8

123.0 g (0.6012 mol) of 3-(3-methyl-2,4-dioxoimidazolidin-1-yl)propionylchloride from Example 7 are dissolved in 1 liter of toluene at 78° C.,and 90.03 g (0.7815 mol) of trimethylsilyl azide are added dropwise tothe solution over the course of 30 minutes. The reaction mixture is thenstirred at 84° C. for 2 hours and subsequently evaporated at 90° C.under reduced pressure in a rotary evaporator, and the residue is driedat 100° C./0.1 mbar, giving 109.4 g (99.3% of theory) of1-(2-isocyanatoethyl)-3-methylimidazolidine-2,4-dione, which is purifiedby fractional distillation and boils at 97°-98° C./0.05 mbar, giving39.5 g (35.8% of theory) of a clear, colourless distillate having anisocyanate content of 5.38 meq of NCO/g (98.5% of theory).

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            45.90    46.05                                                 % H            4.95     4.97                                                  % N            22.94    22.96                                                 ______________________________________                                    

Structure: ##STR49##

EXAMPLE 9

1800 g of Mowiol 6-98 (polyvinyl alcohol from Hoechst AG) are dissolvedin 5 liters of demineralized water at an internal temperature of 80° C.in a glass reactor with ground glass joints fitted with stirrer,thermometer and dropping funnel, 720 g (7.308 mol) of 37% hydrochloricacid are then added over the course of 15 minutes at an internaltemperature of 33°-34° C., and 491.6 g (2.0124 mol) ofN-(2,2-dimethoxyethyl)-3-(2-oxopyrrolidin-1-yl)propionamide (prepared asdescribed in Example 1) are then added dropwise over the course of 1hour. The reaction mixture is stirred at 27°-33° C. for 24 hours andsubsequently neutralized using 740 g (7.308 mol) of triethylamine, andthe dissolved polymer is precipitated using 100 liters of ethanol in anUltra-Turax online Dispax reactor from Janke & Kunkel GmbH & Co. Thesuspension is filtered with suction, and the filter residue is washedwith ethanol and acetone and dried at 60° C. under reduced pressure,giving 1781 g of a colourless, pulverulent polymer:

Analytical data:

Nitrogen content: 2.52%

OH group: 14.68 meq/g

Water content: 2.32% (by the Karl Fischer method)

Structure: ##STR50##

EXAMPLE 10

9.52 g (61.41 mmol) of 2-isocyanatoethyl methacrylate dissolved in 30 mlof anhydrous dimethyl sulfoxide are added dropwise over the course of 15minutes at an internal temperature of 80° C. to a solution of 50 g ofthe polymer (prepared as described in Example 9), 0.2 g of hydroquinonemonomethyl ether, 0.04 g of N,N-dimethylcyclohexylamine and 360 ml ofanhydrous dimethyl sulfoxide in a 750 ml flask with ground glass jointsequipped as described in Example 9, and the reaction mixture is stirredat 80° C. for 5 hours. When the reaction is complete, the polymersolution is precipitated in 4 liters of acetone with vigorous stirringby means of a guide beam stirrer, the resultant suspension is filteredwith suction, and the filter residue is washed with acetone and dried at50° C. under reduced pressure, giving 52.2 g of a pulverulent,colourless polymer having the following analytical data:

Nitrogen content: 3.02% N

OH group: 14.08 meq/g

Double bond: 0.62 mmol of H₂ /g

Structure: ##STR51##

EXAMPLE 11

As described in Example 10, 150 g of polymer prepared as described inExample 9 are dissolved in 1 liter of anhydrous dimethyl sulfoxide, 0.5g of hydroquinone monomethyl ether and 0.15 g ofN,N-dimethylcyclohexylamine are added, and the polymer solution issubsequently reacted, as described in Example 10, with a solution of28.58 g of 2-isocyanatoethyl methacrylate and 100 ml of anhydrousdimethyl sulfoxide. Work-up is carried out as described in Example 10,giving 154.9 g of a colourless polymer. A solution of 150 g of thepolymer described above and 2850 ml of bidistilled water is subjected toultrafiltration (5 KD membrane; 0.23 m²). The purified polymer solutionis precipitated in 10 liters of acetone and filtered with suction, theresultant moist residue is mixed vigorously into 10 liters of acetone,the resultant suspension is filtered with suction, and the filter cakedried under reduced pressure at 50° C., giving 136.7 g (91.1% of theamount employed) of a colourless, pure polymer having the followinganalytical data:

Nitrogen content: 3.17%

OH group: 13.12 meq/g

Double bond: 0.71 meq of H₂ /g

Water content: 2.37% (by the Karl Fischer method)

Structure: ##STR52##

EXAMPLE 12

A mixture of 5.72 g (36.89 mmol) of 2-isocyanatoethyl methacrylate and11.26 g (61.48 mmol) of1-(2-isocyanatoethyl)-3-methylimidazolidine-2,4-dione (prepared asdescribed in Example 8) in 30 ml of anhydrous dimethyl sulfoxide areadded dropwise over the course of 25 minutes with stirring at aninternal temperature of 80° C. to a solution of 50.0 g of Mowiol 6-98(polyvinyl alcohol from Hoechst AG), 350 g of anhydrous dimethylsulfoxide, 0.4 g of hydroquinone monomethyl ether and 0.028 g ofN,N-dimethylcyclohexylamine in a glass apparatus as described in Example9. The mixture is allowed to react for a further 5 hours at an internaltemperature of 80° C., the solution is diluted with 100 ml of acetone,and the polymer is precipitated in 4 liters of acetone. The suspensionis filtered with suction, and the filter residue is washed with acetone,sucked dry and dried at 50° C. to constant weight, giving 60.9 g of thedesired polymer, which has the following analytical data:

Nitrogen content: 4.263% N

OH group: 13.96 meq of OH/g

Double bond: 0.45 meq of C═C/g

Water content: 2.95% (by the Karl Fischer method)

Structure: ##STR53##

EXAMPLE 13

63.6 g of Mowiol 10-98 (polyvinyl alcohol from Hoechst AG), 0.5 g ofhydroquinone monomethyl ether and 1.5 g of dibutyltin dilaurate,dissolved in 430 ml of anhydrous DMSO, are allowed to react with amixture of 7.28 g (46.9 mmol) of 2-isocyanatoethyl methacrylate and 3.33g (46.9 mmol) of ethyl isocyanate in 20 ml of anhydrous DMSO at 80° C.for 5 hours as described in Example 12, and, when the reaction iscomplete, the product is worked up as described in Example 12, giving68.9 g of the desired polymer having the following analytical data:

Nitrogen content: 1.724% N

OH group: 17.08 meq of OH/g

Double bond: 0.62 meq of C═C/g ##STR54##

EXAMPLE 14

13.24 g (116 mmol) 1-methylhydantoin, 19.34 g (140 mmol) waterfreepotassium carbonate and 29.2 g (3-bromo-propionaldehyd-dimethylacetalare allowed to react in 90 ml dimethylsulfoxid for 3 hours and 25minutes at 112°-115° C. The reaction mixture is subsequently cooled to5° C. and filtered with suction. The filtrate is evaporated in a rotaryevaporator and the liquid crude product is purified by fractionaldistillation in vacuo to give 12.44 g (49.6% of theory) liquid3-(3,3-dimethoxy-propyl)-1-methyl-imidazolidin-2,4-dione, having aboiling point of 112°-114° C./0.07 mbar.

Elemental analysis:

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            49.99    50.14                                                 % H            7.46     7.53                                                  % H            12.96    13.10                                                 ______________________________________                                    

Acetal content: 28.535% O--CH₃ (99.4% of theory)

Structur: ##STR55##

EXAMPLE 15

Analogously to example 1, 253.08 g (1.297 mol)3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1-yl)-propionic acid nitrileare hydrolyzed in a solution of 833.1 g 37% hydrochloric acid and 187.8g acetic acid and worked up. The crude product (mixture of acid andammonium chloride) is heated in 750 ml toluene until boiling, filteredwhile hot, and the clear filtrate is cooled to 5° C. The crystallizedacid is isolated and dried at 80°/30 mbar. 249.7 g (91.2% of theory)crystalline 3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1-yl)-propionicacid are obtained which melts at 103° C.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            50.46    50.51                                                 % H            6.59     6.67                                                  % N            13.08    13.10                                                 ______________________________________                                    

Structur: ##STR56##

EXAMPLE 16

A mixture of 10.71 g (50 mmol)3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1yl)-propionic acid(synthetized according to example 15), 31.73 g oxalyl chloride, 25 mlmethylenechloride and 0.5 ml dimethylformamide is stirred for 1 h and 55minutes at 24° C., thereafter evaporated in a rotary evaporator at 70°C. in vacuo, stripped 3 times with about 50 ml of toluene, evaporatedcompletely do dryness and dried at 70° C./10.1 mbar. 11.36 g (97.6% oftheory) of crystalline3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1yl)-propionylchloride areobtained.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            46.46    46.86                                                 % H            5.63     5.85                                                  % N            12.04    11.98                                                 % Cl           15.24    15.19                                                 ______________________________________                                    

Structure: ##STR57##

EXAMPLE 17

19.61 g (84.3 mmol)3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1-yl)-propionylchloride(synthesized according to example 16) and 12.68 g (110 mmol)trimethylsilylazide are allowed to react in 60 ml toluene for 4 hoursand 10 minutes at 88°-95° C. Subsequently the reaction mixture isevaporated and the crude product is purified by fractional distillation.7.98 g (55.9% of theory) of crystalline1-(2-isocyanato-ethyl)-3,5,5-trimethyl-imidazolidin-2,4-dione areobtained which melts at 62° C.

Elemental analysis

    ______________________________________                                                     calculated                                                                           found                                                     ______________________________________                                        % C            51.18    51.34                                                 % H            6.20     6.31                                                  % N            19.89    19.76                                                 ______________________________________                                    

Isocyanate content: 4.55 milli-equivalents NCO/g

Structur: ##STR58##

EXAMPLE 18

To a solution of 37.24 g Mowiol 6-98 (polyvinyl alcohol from HoechstAG), 20 ml 2N hydrochloric acid (40 mmol) and 140 ml water, there isadded dropwise, within 10 minutes at 39° C. inner temperature, asolution of 9.0 g (41.6 mmol)3-(3,3-dimethoxy-propyl)-1-methyl-imidazolidin-2,4-dione (synthesizedaccording to example 14) and 20 ml water and allowed to react for 22hours and 30 minutes. Then 4.05 g (40 mmol) triethylamine are added forneutralisation, the reaction mixture is precipitated in 2 liters ofethanol and isolated by filtration. The moist filter residue is mixedwith 2 liters of ethanol, filtered with suction, which process isrepeated with 2 liters of ethanol and 2 liters of aceton. The filterresidue is dried at 60° C. in vacuo, and 40.3 g of the desired polymerare obtained.

Analytical data:

Nitrogen content: 2.63% N

OH-content: 17.35 milli-equivalents OH/g

Water content: 1.51% H₂ O

Structure: ##STR59##

EXAMPLE 19

30.0 g Polymer (synthesized according to example 18), 0.1 gtriethylamine and 0.2 g hydrochinon-monomethylether are dissolved in 170ml dimethylsulfoxide, heated to 80° C., and within 10 minutes a solutionof 3.57 g (23 mmol) 2-isocyanatoethyl-methacrylate and 10 mldimethylsulfoxide is added dropwise. This mixture is allowed to react 5hours at 80° C., the mixture is then processed according to example 18.30.9 g of a colourless pulverulent polymer are obtained having thefollowing analytical data:

Nitrogen content: 3.22% N

Double Bonds: 0.66 meq C═C/g

OH-Groups: 14.36 milli-equivalents OH/g

Structure: ##STR60##

EXAMPLE 20

Analogously to example 9 a solution of 50.53 g (167.7 mmol)N-(2,2-dimethoxy-ethyl)-3-(3,5,5-trimethyl-2,4-dioxo-imidazolidin-1-yl)-propionicacid amide and 21.34 g (134.1 mmol)2-acrylamido-acetaldehyd-dimethylacetal in 150 ml water are addeddropwise within 15 minutes to 150 g Mowiol 6-98 (polyvinyl alcohol fromHoechst AG), dissolved in 550 ml water and 120 ml 2N hydrochloric acid,and allowed to react at 40° C. for 5 hours. The reaction mixture is thenneutralized with 120 ml 2N NaOH, the neutralized solution is filteredand the clear filtrate is purified by ultrafiltration. The purifiedaqueous polymer solution is introduced into 15 liters of aceton whilevigorously stirring with a stirrer (a so called "Leitstrahlruhrer"), theprecipitated polymer is isolated by filtration and the filter residue isdried under vacuum at 50° C. 182.3 g of a colourless polymer areobtained having the following analytical data:

Nitrogen content: 3.57% N

Water content: 2.84% H₂ O

Double bonds: 0.63 milli-equivalents/g

OH-Groups: 14.52 milli-equivalents/g

Structur: ##STR61##

EXAMPLE 21

200 g Mowiol 6-98 (polyvinyl alcohol from Hoechst AG) are dissolved in600 ml water, then 80 g (0.812 mol) hydrochloric acid 37% are added andfinally 41.4 g (0.2236 mol) 1-(2,2-dimethoxy-ethyl)-pyrrol-2,5-dione areadded within 15 minutes at 30° C. inner temperature. Then the reactionmixture is stirred 25 hours and 45 minutes at 29°-36° C., thenneutralized with 82.17 g (0.812 mol) triethylamine, and the solution istransferred into 15 liters of ethanol with vigorous stirring. Theprecipitated polymer is isolated by filtration, the filter residuewashed with ethanol and aceton and then dried at 50° C. in vacuo. 202.4g of a pulverulent polymer are obtained which is then dissolved in 2.4liters of water and further purified by ultrafiltration. The purifiedpolymer solution is, as described above, precipitated in 10 liters ofaceton, isolated and dried. 148.4 g of the desired polymer are obtainedhaving the following analytical data:

Nitrogen content: 1.20% N

Double bonds: 0.76 milli-equivalents C═C/g

Water content: 2.68% H₂ O

Structur ##STR62##

EXAMPLE 22

Production of contact lenses 0.3% of Irgacure 2059 (based on the polymercontent) is added to a 30% solution of the polymers mentioned inExamples 10 to 13. The solutions are exposed for 6 seconds to a 200 WOriel UV lamp (150 mW/cm²) in a transparent polypropylene contact lensmould. The lenses are removed from the mould. They are transparent andhave very good wearing properties. They are particularly suitable assingle-day lenses, with the further advantage that in principle caresolutions for contact lenses are unnecessary.

What is claimed is:
 1. A process for production of mouldings, whichcomprises the following steps:a) preparation of an essentially aqueoussolution of a water-soluble crosslinkable polymer comprisingcrosslinkable units of the formula XI ##STR63## and at least one furthermodifier comprising units of the formula XII ##STR64## or units of theformula XIII ##STR65## in which U is an ##STR66## or--Y--NH--CO--O--Z--O--CH═CH₂ group, X is a bridge having 2 to 12 carbonatoms,R₂ is hydrogen or a C₁ -C₄ alkyl group, Y is a bridge having 7 to12 carbon atoms, Z is a C₂ -C₁₂ alkylene bridge, which may beinterrupted once or more than once by an oxygen atom, R₃ is hydrogen, aC₁ -C₆ alkyl group or a cycloalkyl group, R is a C₁ -C₁₂ alkylenebridge, R₁ is an organic group having 1 to 18 carbon atoms, A is anorganic radical having 1 to 18 carbon atoms, and m is 0 or 1, b)introduction of the resultant solution into a mould, c) initiation ofthe crosslinking in water or in an organic solvent in which thecrosslinkable polymer is dissolved, and d) opening of the mould so thatthe moulding can be removed.
 2. A process according to claim 1, whereinthe moulding is a contact lens.
 3. A process according to claim 1,wherein the essentially aqueous solution of the water-soluble,crosslinkable polymer comprising crosslinkable units and at least onefurther modifier is free or essentially free from undesiredconstituents, including, monomeric, oligomeric or polymeric startingcompounds used for the preparation of the water-soluble, crosslinkablepolymer, or byproducts formed during the preparation of thewater-soluble, crosslinkable polymer.
 4. A process according to claim 1,wherein the essentially aqueous solution of the water-soluble,crosslinkable polymer comprising crosslinkable units and at least onefurther modifier is used without addition of a comonomer.
 5. A processaccording to claim 1, wherein an initiator for the crosslinking is addedto the solution of the water-soluble, crosslinkable polymer.
 6. Aprocess according to claim 1, wherein the crosslinking is not followedby extraction in order to remove undesired constituents.
 7. A processaccording to claim 1, which comprises the following steps:a) preparationof an essentially aqueous solution of a water-soluble, crosslinkablepolymer comprising units of the formulae XI and XII or XIII which isfree or essentially free from undesired constituents, including,monomeric, oligomeric or polymeric starting compounds used for thepreparation of the polymer, or byproducts formed during the preparationof the polymer, and is used without addition of a comonomer, b)introduction of the resultant solution into a mould, c) initiation ofthe crosslinking, and d) opening of a mould so that the moulding can beremoved.
 8. A process according to claim 7, wherein the moulding is acontact lens.
 9. A process for the production of a contact lensaccording to claim 8, wherein the essentially aqueous solution is apurely aqueous solution or a solution in an artificial tear fluid.
 10. Aprocess for the production of a contact lens according to claim 8,wherein a crosslinking initiator is added to the solution, and thecrosslinking is carried out by photocrosslinking.
 11. A contact lens,obtained by a process according to claim
 1. 12. A contact lens accordingto claim 11, which is suitable for its intended use without extraction.13. A contact lens obtained according to claim 8, which is suitable forits intended use without extraction.
 14. A crosslinkable polymercomprising units of the formulae XI and XII, XI and XII or XI, XII andXIII ##STR67## in which U is an ##STR68## or--Y--NH--CO--O--Z--O--CH═CH₂ group, X is a bridge having 2 to 12 carbonatoms,R₂ is hydrogen or a C₁ -C₄ alkyl group, Y is a bridge having 7 to12 carbon atoms, Z is a C₂ -C₁₂ alkylene bridge, which may beinterrupted once or more than once by an oxygen atom, R₃ is hydrogen, aC₁ -C₆ alkyl group or a cycloalkyl group, R is a C₁ -C₁₂ alkylenebridge, R₁ is an organic group having 1 to 18 carbon atoms, A is anorganic radical having 1 to 18 carbon atoms, and m is 0 or
 1. 15. Acrosslinkable polymer according to claim 14, which is a derivative of apolyvinyl alcohol having a molecular weight of at least about 2000comprising from about 0.5 to about 80%, based on the number of hydroxylgroups in the polyvinyl alcohol, of units of the formulae XI and XII, XIand XIII or XI, XII and XIII.
 16. A crosslinkable polymer according toclaim 15, which comprises units of the formula V ##STR69## or of theformula VII ##STR70## or of the formula IX ##STR71## or of the formula X##STR72##
 17. A crosslinkable polymer according to claim 16, whichcomprises units of the formula V or of the formula IX.
 18. Acrosslinkable polymer according to claim 16, which comprises units ofthe formula V, in which:R₃ is hydrogen or a CH₃ or C₂ H₅ group, R is aC₁ -C₃ alkylene bridge, m is 0, R₁ is the radical of a heterocycliccompound, X is an aliphatic bridge having 2 to 12 carbon atoms, R₂ ishydrogen or CH₃.
 19. A crosslinkable polymer according to claim 16,which comprises units of the formula VII, in which:R₃ is hydrogen or aCH₃ or C₂ H₅ group, R is a C₁ -C₃ alkylene bridge, m is 0, R₁ is aradical of a heterocyclic compound, Y is a C₇ -C₁₂ aromatic radical, andZ is a C₂ -C₄ alkylene bridge.
 20. A crosslinkable polymer according toclaim 16, which comprises units of the formula IX, in which:A is analiphatic radical having 1 to 18 carbon atoms, X is an aliphatic bridgehaving 2 to 12 carbon atoms, and R₂ is hydrogen or CH₃.
 21. Acrosslinkable polymer according to claim 20, in which A is C₁ -C₆ alkyl,above.
 22. A crosslinkable polymer according to claim 16, whichcomprises units of the formula X, in whichA is an aliphatic radicalhaving 1 to 18 carbon atoms, Y is an aromatic radical having 7 to 12carbon atoms, and Z is a C₂ -C₄ alkylene bridge.
 23. A crosslinkedpolymer obtainable by photocrosslinking a crosslinkable polymeraccording to claim 14, in the presence or absence of an additionalvinylic comonomer.
 24. A crosslinked polymer obtained byphotocrosslinking a crosslinkable polymer according to claim 14 inessentially pure form, in the presence or absence of an additionalvinylic comonomer.
 25. A crosslinked polymer according to claim 24,where the crosslinkable polymer is converted into essentially pure formby single or repeated ultrafiltration.
 26. A crosslinked polymerobtainable by photocrosslinking a crosslinkable polymer according toclaim 14 in the absence of an additional vinylic comonomer.
 27. Acrosslinked polymer obtained by photocrosslinking a crosslinkablepolymer according to claim 14 in the presence of from 0.5 to 80 units ofan additional vinylic comonomer per unit of formula XI.
 28. A processfor the preparation of a crosslinked polymer, which comprisesphotocrosslinking a crosslinkable polymer according to claim 14 in thepresence or absence of an additional vinylic comonomer.
 29. A processaccording to claim 28, wherein the crosslinkable polymer is employed inessentially pure form.
 30. A process according to claim 29, wherein thecrosslinkable polymer is converted into essentially pure form by singleor repeated ultrafiltration.
 31. A process according to claim 28,wherein the photocrosslinking is carried out in aqueous solution.
 32. Aprocess according to claim 28, wherein the photocrosslinking is carriedout in an organic solution in which the crosslinkable polymer isdissolved.
 33. A process according to claim 32, wherein thephotocrosslinking is carried out in dimethyl sulfoxide.
 34. A mouldingcomprising a crosslinked polymer according to claim
 23. 35. A mouldingaccording to claim 34, wherein the moulding is a contact lens.
 36. Aprocess for the production of a moulding, which comprisesphotocrosslinking a crosslinkable polymer according to claim 14 in aclosed mould in the presence or absence of an additional vinyliccomonomer.
 37. A process for the production of a contact lens, whichcomprises photocrosslinking a crosslinkable polymer according to claim14 in a closed contact-lens mould by the full-mould method in thepresence or absence of an additional vinylic comonomer.
 38. A processaccording to claim 4, wherein the essentially aqueous solution of thewater-soluble, crosslinkable polymer comprising crosslinkable units andat least one further modifier is used without addition of a vinyliccomonomer.
 39. A crosslinkable polymer according to claim 19, wherein Yis ##STR73##
 40. A crosslinkable polymer according to claim 20, whereinA is ethyl or isopropyl.
 41. A crosslinkable polymer according to claim22, wherein Y is ##STR74##
 42. A crosslinked polymer according to claim27, wherein the additional vinylic comonomer is present from 1 to 30units.
 43. A crosslinked polymer according to claim 27, wherein theadditional vinylic comonomer is present from 5 to 20 units.